Bulletin d’avalanche

Kootenay Boundary

Dec 19, 2018Avalanche Canada
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Archivé · expiré 8 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

The load continues to grow on a weak layer buried in early December. As a result this persistent slab is primed for human triggering and a conservative approach is recommended.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–3
    A weak layer buried around 70 cm is the primary concern. This concern is heightened on steep slopes where wind has drifted snow into a reactive slab.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    Recent new snow and strong winds have set up wind slabs in exposed areas, particularly on north to east aspects. With more than 20 cm of new snow in the past 24 hours, steeper slopes and rolls on all aspects are also suspect!

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

TUESDAY NIGHT: Flurries, accumulation 5-10 cm. Alpine temperature -2. Moderate to strong southwest wind. Freezing level 1400 m.WEDNESDAY: Isolated flurries. Alpine temperature -4. Light west wind. Freezing level 1200 mTHURSDAY: Snow, accumulation 15-25cm. Alpine temperature -1. Moderate to strong southwest wind. Freezing level 1500 m.FRIDAY: Cloudy with sunny breaks. Alpine temperature -7. Light west wind.  Freezing level at the valley bottom.

Avalanche Summary

Recent reports indicate explosives controlled and natural storm slab avalanches running to size 2 on Monday on a variety aspects at tree line and in the alpine.

Snowpack Summary

The primary concern in the snowpack is the layer below last week's storm snow accumulations; that would be the Dec 09 (date it was buried) layer of facets (sugary crystals), surface hoar (feathery crystals) and a sun crust on south aspects all about 60 cm deep. After the latest storm Monday night into Tuesday, the Dec 09 will be 70-80 cm below the surface, as well as some new storm & wind slab issues (say within 30 cm of the surface, deeper in wind loaded pockets). Although 10 or 15 cm of new snow daily often won't start a natural avalanche cycle, it looks like we're getting real close to tipping the balance. The Dec 09 layer, it's primed; recent "sudden" snowpack test results and remotely triggered avalanches indicate it remains a critical layer. If the forecast storms materialize I expect this layer may wake up as we continue to build the load on top of it.Lower in the snowpack, previous weak layers from November appear inactive. These deeper layers could possibly cause problems on cold (north facing) slopes at high elevations where the snowpack is thin, but in most places, this is unlikely.

Régions couvertes